INDICATOR SIGNIFICANCE OF NATIVE VEGETATION 287 



mined. The studies of the depth and character of the root systems 

 will lead to the determination of the different successional stages 

 of the native vegetation on burned-over or cut-over land. It is 

 very probable that the sudden removal of the vegetative cover 

 renders the site less favorable for the successful establishment 

 and optimum development of the climax species and the more 

 favorable for the invasion of species normally occurring on 

 poorer sites at lower elevations. 



The fundamental study of forest planting sites logically re- 

 solves itself into three categories: (1) the empirical establish- 

 ment of plantations and the observation and study of their 

 survival and subsequent development, (2) the measurement and 

 study of the most important physical factors of the site, such as 

 the available soil moisture or growth water and evaporation, 

 and (3) the indicator significance of the native vegetation occur- 

 ring on the sites implying a very careful correlation of all three 

 phases, especially the correlation of the species with the physical 

 conditions which produce them, and a study of the relative 

 transpiration of the natural and planted vegetation. 



It is readily conceivable that site studies of this character 

 will be of the utmost value in explaining the presence or absence 

 of tree growth on certain areas, in the judicious selection of the 

 proper species and sites in the reforestation of much of the 

 denuded forest land of the United States, and in establishing a 

 working basis for the classification of the potential productivity 

 of forest lands. Only after considering the relative agricultural 

 and forest productivity of the land on a combined scientific 

 and economic basis, can a positive conclusion be reached that 

 its greatest utility lies in its use for forestry or fcr agricultural 

 purposes. 



